Relationship between the size of Pseudamphithoides bacescui (Amphipoda, Gammaridea) and the size of pods of algae

The ampithoids are benthic amphipods that are related to algae in shallow water. The aim of the present study was to determine, for the first time, the relationship between the size of Pseudamphithoides bacescui and the size of the leaves of algae used for the construction of the shelter in the Sisal Reef System, Mexico. The organisms were recovered manually, using SCUBA. The amphipods were collected from a ‘pod’ cut from the blades of foliaceous algae and coral rubble. The length and width of the pods were also measured in micrometers. Forty-one specimens of P. bacescui were collected. The amphipods were found in pods of Dictyopteris delicatula and Dictyota cervicornis. The average total length of males of P. bacescui in D. delicatula was 661.89 ± 347.23 µm; the average length of females was 493.79 ± 237.16 µm. The average total length of the males in D. cervicornis was less than 163.93 ± 53.22 µm. The regression between the length and width of P. bacescui against the length and width of the leaf or pod of the alga showed a positive and significant relationship. Smaller individuals were found in D. cervicornis, and a larger size was found in D. delicatula. This study defined a mesograzer intraspecific variation in size, which has a great importance in the ecological dynamics of the host plant.